1. Field of the Invention
The present invention relates to a process for the production of 1-amino-1-methyl-3(4)-aminomethylcyclohexane (AMCA), the precursor for the production of 1-isocyanato-1-methyl-3(4)-isocyanatomethylcyclohexane (IMCI).
2. Description of the Prior Art
DE-A 4,401,929 describes a process for the production of 1-amino-1-methyl-3(4)-aminomethylcyclohexane (AMCA) that may be illustrated by the following reaction scheme: ##STR1##
According to this reaction mechanism, 4(5)-cyano-1-methylcyclohexene (CMC) serving as starting product is caused to react with hydrocyanic acid in the presence of sulphuric acid in a Ritter reaction to form 1-formamido-1-methyl-3(4)-cyanocyclohexane (FMC). In a further reaction step the 1-formamido-1-methyl-3(4)-cyanocyclohexane (FMC) is hydrolyzed in the acidic state to form 1-amino-1-methyl-3(4)-cyanocyclohexane (AMC), which is then hydrated to form 1-amino-1-methyl-3(4)-aminomethylcyclohexane (AMCA). In order to obtain high selectivities for the formation of FMC during the Ritter reaction, a considerable excess of hydrocyanic acid is required, which means that this process can only be operated only with considerable safety measures.
European patent application EP-A 0,153,561 describes a process for the production of 1-amino-1-methyl-3(4)-aminomethylcyclohexane (AMCA) by the following reaction scheme: ##STR2##
In this process the Ritter reaction (1) is carried out by introducing 4(5)-aminomethyl-1-methylcyclohexene (CMA) into sulphuric acid and then charging hydrocyanic acid to this reaction mixture at 10.degree. to 50.degree. C. Even after four hours about 13% of 3(4)-aminomethyl-1-methylcyclohexanol (AA) is obtained which can only be separated by distillation from the 1-amino-1-methyl-3(4)-aminomethylcyclohexane (AMCA) with difficulty (see Example 1a from EP-A 0,153,561). For the subsequent hydrolysis reaction (2), reaction-times of three hours are required in accordance with the described process. Because of the long reaction-times that are required for the Ritter reaction (1) and hydrolysis reaction (2), this process is associated with considerable investment and energy costs.
In European Patent EP-A 0,153,561, it is also possible to use 3(4)-aminomethyl-1-methylcyclohexanol (M) as the starting material for the Ritter reaction (1). However, the selectivity achieved in this case is only about 75%. Consequently an overall selectivity of about 81% is obtained in accordance with EP-A 0,153,561.
It is an object of the present invention to provide a process for the production of 1-amino-1-methyl-3(4)-aminomethylcyclohexane (AMCA) from 4(5)-aminomethyl-1-methylcyclohexene (CMA) in which short reaction-times and high selectivities are achieved and in which clear economic advantages are obtained in comparison with the previously described processes.
This object may be achieved in accordance with the process of the present invention which is described hereinafter.